A colleague mentioned the Free produce moment, a boycott action started around 1780 by quakers to avoid the consumption of anything that had required slave labour (it started with sugar and rum!). In 1791, William Fox wrote: “A family that uses only 5lb. of sugar per week, with the proportion of rum, will, by abstaining from the consumption 21 months, prevent the slavery or murder of one fellow creature; eight such families in 19 1/2 years, prevent the slavery or murder of 100, and 38,000 would totally prevent the Slave-Trade to supply our islands ... in every pound of sugar used, the produce of slaves imported from Africa, we may be considered as consuming two ounces of human flesh.” The urge to boycott spread in 19th century, either through humanistic societies, or through some merchants (such as the British India Society) who supported free-produce. In the end, it was not so successful: ”Benefits to slaves or reduction in demand for slave-produced goods was minuscule. Many abolitionists ignored the issue altogether. Though William Lloyd Garrison, founder of the American Anti-Slavery Society, initially proclaimed at a convention in 1840 that his wool suit was made without slave labor, he later examined the results of the movement and criticized it as impossible to enforce, ineffective, and a distraction from more important tasks.” https://en.wikipedia.org/wiki/Free-produce_movement